This invention relates generally to updating modulated data signals in an optical network. Specifically, this invention relates to updating a modulated optical data signal having high data rate signal and subcarrier signal components by superimposing an updated subcarrier signal onto the modulated optical data signal. A drop/insert facility is utilized to create the updated optical signal without having to alter the high data rate signal component of the modulated optical data signal.
2. Related Art
A typical communication network, serving to transport information among a number of locations, consists of various physical sites, called nodes, interconnected by information conduits, called "links." Each link serves to carry information from one site to another site. Individual sites contain equipment for combining, separating, transforming, conditioning, and/or routing data.
FIG. 1 shows an example typical communications network 100 consisting of sites 101-105 connected by links 120-121. Links are generally implemented using electrical cables, satellites, radio or microwave signals, or optical connections and can stretch for tens or hundreds of miles between sites. Through these links, the communications network 100 carries data signals among the sites 101-105 to effectively interconnect data remote equipments 111-115, i.e., computers, remote terminals, servers, etc. One or more links 120 and 121 that connect two sites are collectively referred to as a span 130. These sites 101-105 normally contain at least one cross-connect switch (either electrical or optical) and are in constant communication with a central network management system facility 140 which monitors the flow of traffic throughout the network.
Optical networks that include a plurality of optical transmission lines or links permit high bandwidth data communications, and may be used in telephone and other data network systems. High speed data can be modulated on light waves which are transmitted through the optical network. The optical transmission line, connecting an optical transmitter and receiver, can propagate many light wave signals of different frequencies simultaneously. Thus, fiber optic communications links carry vast amounts of information among distant sites to accomplish data, voice and image connectivity over a large geographical area.
The traffic of even a single link represents a formidable volume of vital data, equivalent to tens of thousands of phone calls. Sudden failure of a data link can cause a significant loss in revenues for a network owner and loss of commerce and other benefits for the network subscribers. Consequently, restoration techniques have been devised to quickly circumvent network link failures and restore normal traffic flow.
Thus, a primary concern for network providers is that with the substantial volume of data traffic and re-routing techniques performed as a result of restoration events, it has become increasingly important to accurately track and "label" optical data streams traveling through various portions of the network.